Re: [PATCH DNM RFC 13/16] arm64: dts: qcom: sm8650: Describe clock controller power rails

[Konrad Dybcio]

On 10/14/26 4:33 PM, Dmitry Baryshkov wrote:
> On Wed, Oct 14, 2026 at 04:20:08PM +0200, Konrad Dybcio wrote:
>> On 10/14/26 4:19 PM, Dmitry Baryshkov wrote:
>>> On Wed, Oct 14, 2026 at 02:19:13PM +0200, Konrad Dybcio wrote:
>>>> From: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
>>>>
>>>> The SM8650 clock-controller nodes omit rails needed by their clocks and
>>>> PLLs. Without those connections, the clock-owned DVFS implementation
>>>> cannot attach its voters to all required domains and controller probe
>>>> can fail before any clocks are registered.
>>>>
>>>> Fixes: d2350377997f ("arm64: dts: qcom: add initial SM8650 dtsi")
>>>> Assisted-by: LLM
>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxxxx>
>>>> ---
>>>>  arch/arm64/boot/dts/qcom/sm8650.dtsi | 16 +++++++++++-----
>>>>  1 file changed, 11 insertions(+), 5 deletions(-)
>>>>
>>>> @@ -6049,8 +6055,8 @@ dispcc: clock-controller@af00000 {
>>>>  				 <0>, /* dp3 */
>>>>  				 <0>;
>>>>  
>>>> -			power-domains = <&rpmhpd RPMHPD_MMCX>;
>>>> -			required-opps = <&rpmhpd_opp_low_svs>;
>>>
>>> I think this is neccessary (at least on some platforms) to keep MMCX out
>>> of retention. Even if we can drop it here, I don't think we can drop it
>>> for older platforms.
>>
>> MMCX exists precisely to let you turn it off, the clock patches
>> retain a way to keep the clock on during the runtime-resume of
>> the clock controller driver
> 
> Turning off MMCX is possible together with suspending the dispcc. If
> dispcc is resumed, MMCX should be at least low_svs. On some platforms
> it's handled by the cmd-db, where MMCX has a minimal value of low_svs.
> On other platforms MMCX lists 'RET' as a possible value, however it's
> not enough for dispcc (or other CCs) to work. In theory, *I think*, it's
> exactly what 'GCC_DISP_AHB_CLK' might need to vote, but we don't
> represent it.

Retention isn't a ""real"" state the OS should vote for, as the HW
downstream of the rails generally needs some flavor of LOW_SVS to
function, or at least I don't know of any such cases.

See also

7178817f1904 ("pmdomain: qcom: rpmhpd: Skip retention by default")

Konrad